Surgical instruments employing sensors

ABSTRACT

According to an aspect of the present disclosure, a surgical instrument for operating on tissue is provided. The surgical instrument includes an end effector including a first tissue engaging member and a second tissue engaging member in juxtaposed relation to the first tissue engaging member; a gap determination element operatively associated with each of the first tissue engaging member and the second tissue engaging member for measuring a gap distance between the first tissue engaging member and the second tissue engaging member; and a tissue contact determining element operatively associated with a respective tissue contacting surface of at least one of the first tissue engaging member and the second tissue engaging member. The present disclosure also relates to methods of using the surgical instrument.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a Continuation application which claims thebenefit of and priority to U.S. patent application Ser. No. 12/760,635,filed Apr. 15, 2010 (U.S. Patent Application Publication No.2010/0200637), which is a Divisional application which claims thebenefit of and priority to U.S. patent application Ser. No. 11/444,548,filed May 31, 2006 (U.S. Pat. No. 7,717,312), which claims the benefitof and priority to each of U.S. Provisional Application No. 60/687,243,filed Jun. 3, 2005, and U.S. Provisional Patent Application Ser. No.60/687,214, filed on Jun. 3, 2005, the entire contents of each of whichbeing incorporated herein by reference.

BACKGROUND

1. Technical Field

The present disclosure relates to surgical instruments and, moreparticularly, to mechanical, electro-mechanical and energy-basedsurgical instruments and systems.

2. Background of Related Art

Surgical instruments used in open and minimally invasive surgery arelimited in their ability to sense and/or control conditions and/orparameters and factors critical to effective operation. For example,conventional surgical instruments cannot measurably detect the amount oftissue positioned between tissue contacting surfaces of an end effectorof the surgical instrument, the clamping force being exerted on thetissue, the distance between juxtaposed tissue contacting surfaces,and/or the viability of the tissue clamped therebetween.

Accordingly, a need exists for surgical instruments and/or systems thatcan sense a multitude of parameters and factors at the target surgicalsite, such as, for example, the distance between juxtaposed tissuecontacting surfaces of the surgical instrument, the amount of tissuepositioned between tissue contacting surfaces of an end effector of thesurgical instrument, the clamping force being exerted on the tissue,and/or the viability of the tissue clamped therebetween.

A need exists for surgical instruments and/or systems which can,according to the conditions sensed and/or measured at the targetsurgical site, utilize, display, record and/or automatically control theposition of the tissue contacting surfaces of the surgical instrumentand/or system, alert a surgeon prior to operation of the surgicalinstrument and/or system, and/or operate the surgical instrument and/orsystem.

SUMMARY

According to an aspect of the present disclosure, a surgical instrumentfor operating on tissue is provided. The surgical instrument includes anend effector including a first tissue engaging member and a secondtissue engaging member in juxtaposed relation to the first tissueengaging member; a gap determination element operatively associated witheach of the first tissue engaging member and the second tissue engagingmember for measuring a gap distance between the first tissue engagingmember and the second tissue engaging member; and a tissue contactdetermining element operatively associated with a respective tissuecontacting surface of at least one of the first tissue engaging memberand the second tissue engaging member.

The surgical instrument may further include a processor operativelyconnected to the gap determination element and to each of the tissuecontact determining elements. Each of the first and second tissueengaging elements includes at least one tissue contact determiningelement supported on the tissue contacting surface thereof.

The gap determination element may be selected from the group consistingof a slide potentiometer, a rotational potentiometer, a linear variabledifferential transformer, a magneto-resistive element, capacitiveelements, electromagnetic induction sensors, Hall effect sensors, andoptical based sensors.

The tissue contact determining element may be selected from the groupconsisting of pressure sensors, electrical contacts and sensingcircuits, force transducers, piezoelectric elements, piezoresistiveelements, metal film strain gauges, semiconductor strain gauges,inductive pressure sensors, capacitive pressure sensors, andpotentiometric pressure transducers.

The surgical instrument may be a stapler.

The tissue contact determining element may transmit a signal to theprocessor when a tissue is positioned between the first and secondtissue engaging elements and when the tissue contacting surface of eachof the first and second tissue engaging elements contacts the tissue.The signal transmitted to the processor, when the tissue contactingsurface of each of the first and second tissue engaging elementscontacts the tissue, may be the initial tissue thickness.

The processor may be configured to monitor at least one of a compressionforce and a strain on the tissue as the tissue is compressed between thefirst and second tissue engaging members. The processor may beconfigured to activate a signal when at least one of the compressionforce and strain on the tissue achieves a predetermined level ofcompression or strain. The processor may also be configured to activatea signal when a tissue contact determining element engages at least oneof a first and second tissue.

The predetermined level of compression or strain on the tissue ismaintained in a data look-up table. The data look-up table may includepredetermined levels of compression or strain for numerous tissue types.The predetermined level of compression or strain may be a percentage ofthe initial tissue thickness.

According to another aspect of the present disclosure, a method ofperforming a surgical procedure on tissue is provided. The methodincludes the steps of providing a surgical instrument including an endeffector including a first tissue engaging member and a second tissueengaging member in juxtaposed relation to the first tissue engagingmember; positioning the first and second tissue engaging members onopposite sides of the tissue; approximating the first and second tissueengaging members until the tissue contact determining element isengaged; recording an initial distance between the first and secondtissue engaging members as an initial tissue thickness; furtherapproximating the first and second tissue engaging members to compressthe tissue therebetween; monitoring at least one of a compression forceand a strain on the tissue; and terminating the approximation of thefirst and second tissue engaging members when at least one of thecompression force and the strain on the tissue reaches a predeterminedlevel.

The surgical instrument may include a gap determination elementoperatively associated with each of the first tissue engaging member andthe second tissue engaging member for measuring a gap distance betweenthe first tissue engaging member and the second tissue engaging member;and a tissue contact determining element operatively associated with arespective tissue contacting surface of at least one of the first tissueengaging member and the second tissue engaging member.

The surgical instrument may further include a processor operativelyconnected to each of the gap determining elements and tissue contactdetermining elements. The tissue contact determining elements maytransmit a signal to the processor when the first and second tissueengaging members are in contact with the tissue. The gap determiningelements may transmit signals to the processor regarding a distancebetween the first and second tissue engaging members.

The method may further include the step of determining at least one ofthe compression force and strain on the tissue as a result of thereduction in distance between the first and second tissue engagingmembers.

The method may further include the step of activating an indicator whenat least one of the compression force and strain on the tissue achievesthe predetermined level of compression or strain. The method may stillfurther include the step of setting the predetermined level ofcompression or strain for the tissue prior to the compression of thetissue.

The surgical instrument may be a stapler.

The method may further include the step of firing the surgical staplerwhen at least one of the compression force and the strain on the tissueis approximately equal to the predetermined level of compression orstrain.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of this specification, illustrate embodiments of the presentdisclosure and, together with the detailed description of theembodiments given below, serve to explain the principles of thedisclosure.

FIG. 1 is a perspective view of a surgical instrument according to anembodiment of the present disclosure;

FIG. 2 is an enlarged perspective view, partially cut away, of theindicated area of detail of FIG. 1;

FIG. 3 is a schematic cross-sectional view as taken along section lines3-3 of FIG. 2;

FIG. 3A s a schematic cross-sectional view as taken along section lines3-3 of FIG. 2, illustrating an alternate embodiment of the presentdisclosure;

FIG. 4 is a side, longitudinal cross-sectional view of the surgicalinstrument of FIG. 1, shown in a first condition;

FIG. 4A is an enlarged schematic illustration of a position sensor ofthe surgical instrument of FIG. 1, shown in a first condition;

FIG. 5 is a side, longitudinal cross-sectional view of the surgicalinstrument of FIG. 1, shown in a second condition;

FIG. 5A is an enlarged schematic illustration of the position sensor ofthe surgical instrument of FIG. 1, shown in a second condition;

FIG. 6 is a side, longitudinal cross-sectional view of the surgicalinstrument of FIG. 1, shown in a third condition;

FIG. 6A is an enlarged schematic illustration of the position sensor ofthe surgical instrument of FIG. 1, shown in a third condition;

FIG. 7 is a perspective view of a surgical instrument according toanother embodiment of the present disclosure;

FIG. 8 is a top perspective view of the top of the handle assembly ofthe surgical instrument of FIG. 7 with a handle section removedtherefrom;

FIG. 9 is a side cross-sectional view of the distal end of the surgicalinstrument of FIGS. 7 and 8, shown in a first condition;

FIG. 10 is a side cross-sectional view of the distal end of the surgicalinstrument of FIGS. 7 and 8, shown in a second condition;

FIG. 11 is a side cross-sectional view of the distal end of the surgicalinstrument of FIGS. 7 and 8, shown in a third condition;

FIG. 11A is a side cross-sectional view of the distal end of thesurgical instrument of FIGS. 7 and 8, illustrating the operation of aplunger sensor thereof;

FIG. 12 is a perspective view of a surgical instrument according to yetanother embodiment of the present disclosure;

FIG. 13 is a side cross-sectional view of the surgical instrument ofFIG. 12, taken along the longitudinal axis, depicting the coupling ofthe cartridge receiving half-section with the anvil half-section;

FIG. 14 is side cross-sectional view of the surgical instrument of FIGS.12 and 13, taken along the longitudinal axis, shown in a closedpre-firing condition;

FIG. 15 is a perspective view of a surgical instrument according to yetanother embodiment of the present disclosure;

FIG. 16 is a side, cross-sectional view of the surgical instrument ofFIG. 15, shown in a first, unapproximated condition;

FIG. 17 is an enlarged, side cross-sectional view of a tool assembly ofthe surgical instrument of FIGS. 15 and 16, shown in the first,unapproximated condition;

FIG. 18 is an enlarged, side cross-sectional view of a tool assembly ofthe surgical instrument of FIGS. 15 and 16, shown in a second,approximated condition;

FIG. 19 in an enlarged, side cross-sectional view of a tool assembly ofthe surgical instrument of FIGS. 15 and 16, shown after completion of afiring stroke; and

FIG. 20 is a schematic illustration of a tissue contact circuit showingthe completion of the circuit upon contact with tissue a pair of spacedapart contact plates.

DETAILED DESCRIPTION OF EMBODIMENTS

Preferred embodiments of the presently disclosed surgical instrumentsand systems will now be described in detail with reference to thedrawing figures wherein like reference numerals identify similar oridentical elements. As used herein and as is traditional, the term“distal” will refer to that portion which is further from the user whilethe term “proximal” will refer to that portion which is closer to theuser.

A surgical instrument in accordance with an embodiment of the presentdisclosure is shown generally as 10 in FIGS. 1-6A. Surgical instrument10 includes a body 12 defining a stationary handle 14, a pivotabletrigger 16, an elongated central body portion 18, and an end effectorincluding a first member or cartridge assembly 20 and a second member ofanvil assembly 22. A thumb button 24 is slidably positioned on each sideof body 12. Thumb buttons 24 are movable to manually advance analignment pin assembly (not shown). A release button 150 is positionedon the proximal end of body 12 and is depressible to allow cartridgeassembly 20 to return from an approximated position disposed adjacent toanvil assembly 22 to a position spaced from anvil assembly 22 (asshown).

Referring to FIG. 2, surgical stapling instrument 10 includes a pair ofclamp slide members 66 a and 66 b, an alignment pin pusher 68 slidablyinterposed between clamp slide members 66 a and 66 b, and a thrust bar70 slidably interposed between alignment pin pusher 68 and clamp slidemember 66 b. Clamp slide members 66 a and 66 b, alignment pin pusher 68and thrust bar 70 are slidably supported between frame members 28 a and28 b for movement between retracted and advanced positions in responseto movement of trigger 16 through an approximation stroke and/or afiring stroke.

As seen in FIGS. 1 and 2, a gap measurement element or device 50 isoperatively supported on frame member 28 b. In particular, gapmeasurement device 50 is secured to frame member 28 b. Gap measurementdevice 50 is configured and adapted to measure and convey to the userthe distance between cartridge assembly 20 and anvil assembly 22 duringthe surgical procedure.

Gap measurement device 50 may be, for example, a slide potentiometer, arotational potentiometer (see FIG. 3A), or the like. As best seen inFIG. 3, gap measurement device 50 includes a body portion 52 secured toa surface of frame member 28 b and a wiper 54, extending through anelongate slot 29 formed in frame member 28 b, operatively connected toclamp slide member 66 b. Wiper 54 is slidably supported in body portion52 such that as wiper 54 moves along the length of body portion 52 (inthe direction of double-headed arrow “B”) a different impedance iscreated and thus a different current (or voltage) may be transmitted toa control unit (not shown). Wiper 54 is desirably fixedly connected toclamp slide member 66 b. In this manner, as clamp slide member 66 b isaxially displaced with respect to frame member 28 b, wiper 54 is axiallydisplaced with respect to body portion 52, thereby altering and/orchanging the impedance value of gap measurement device 50.

As seen in FIG. 3A, the gap measurement device 50 may be in the form ofa rotational potentiometer including a gear or pinion 54 a operativelysupported on frame member 28 b and a rack 52 b or the like formed in/onor supported on clamp slide member 66 b, wherein pinion 54 b isoperatively engaged with rack 52 b. In operation, as clamp slide member66 b moves, proximally or distally, relative to frame member 28 b rack52 b causes pinion 54 b to rotate clockwise or counter-clockwise therebyvarying the current or voltage.

Operation of surgical instrument 10 will now be described with referenceto FIGS. 4-6A. It is noted that the movements of the various componentsof surgical instrument 10 will be described from the vantage point ofone viewing the instrument as positioned in the referenced FIG.

FIGS. 4 and 4A illustrate surgical instrument 10 prior to use. Asillustrated, cartridge assembly 60 and anvil assembly 62 are in spacedrelation, trigger 16 is in the non-compressed position, and clamp slides66 a and 66 b and thrust bar 70 are in the retracted position. Whenclamp slide 66 b is in the retracted position, wiper 54 of gapmeasurement device 50 is positioned rearwardly within slot 29 of framemember 28 b. With wiper 54 of gap measurement device 50 in the retractedposition, a unique voltage is generated and measured by a processor (notshown) which indicates to the processor that cartridge assembly 60 andanvil assembly 62 are in spaced relation to one another.

FIGS. 5 and 5A illustrate surgical instrument 10 during theapproximation stroke of trigger 16. As illustrated, trigger 16 is movedin the direction indicated by arrow “A” to effectively move front link112 forwardly and to move clamp slides 66 a and 66 b forwardly throughpin 88. As seen in FIG. 5A, as clamp slide 66 b is moved forwardly,wiper 54 of gap measurement device 50 is also moved forwardly relativeto body portion 52, thereby varying the voltage generated by gapmeasurement device 50. As wiper 54 of gap measurement device 50 is movedforwardly relative to body portion 52, thereby varying the voltagegenerated and measured by the processor, the distance between cartridgeassembly 20 and anvil assembly 22 may be determined.

FIGS. 6 and 6A illustrate surgical instrument 10 in the fullyapproximated position with trigger 16 in the compressed position. Asillustrated, trigger 16 has been fully approximated, thereby fullyadvancing clamp slides 66 a and 66 b such that cartridge assembly 20 andanvil assembly 22 are in the approximated position. Concomitantlytherewith, wiper 54 of gap measurement device 50 is advanced to aforward most position within slot 29 of frame member 28 b. With wiper 54of gap measurement device 50 in a distal-most position, a unique voltageis generated and measured by the processor which indicates to theprocessor that cartridge assembly 20 and anvil assembly 22 are in theapproximated position.

Turning now to FIGS. 1 and 4-6A, surgical instrument 10 includes aplurality of contact sensors 60 placed along the length of a tissuecontacting surface of each of cartridge assembly 20 and anvil assembly22. Contact sensors 60 are connected to the processor or CPU and provideindication as to when an object, such as, tissue, is located betweencartridge assembly 20 and anvil assembly 22 and in contact therewith.Contact sensors 60 function to determine an initial thickness of thetissue interposed between cartridge assembly 20 and anvil assembly 22.This initial tissue thickness defines a zero point of reference.

According to a method of operation, with cartridge assembly 20 and anvilassembly 22 in spaced relation to one another, target tissue is placedtherebetween. With the target tissue positioned between cartridgeassembly 20 and anvil assembly 22, cartridge assembly 20 and anvilassembly 22 are approximated towards one another until the target tissuemakes contact with the contact sensors 60. At this time, the distancebetween cartridge assembly 20 and anvil assembly 22 is measured and/orrecorded. This initial distance between cartridge assembly 20 and anvilassembly 22 is recorded as the initial thickness of the tissue or thezero point of reference. With the contact distance between cartridgeassembly 20 and anvil assembly 22 or the initial tissue thicknessrecorded, the cartridge assembly 20 and the anvil assembly 22 arefurther approximated until a desired gap between the cartridge assembly20 and the anvil assembly 22 is obtained. Once the desired gap betweenthe cartridge assembly 20 and the anvil assembly 22 is achieved, thisdistance is recorded as the compressed tissue thickness.

Alternatively, following the determination of the initial thickness ofthe tissue, a predetermined value for the compression and/or strain ofthe tissue may be set on the processor or CPU. The predetermined valueof the compression and/or strain may be obtained from a data look-uptable or the like for the particular tissue being compressed.Accordingly, as the cartridge assembly 20 and the anvil assembly 22 areapproximated toward one another, thereby reducing the gap therebetween,the compression and/or strain of the tissue is continually monitoreduntil the compression and/or strain on the tissue achieves thepredetermined value. At such a time, a sensor indicator may be activated(e.g., a light, a tone, etc.) to advise the user that the predeterminedvalue for the compression and/or strain has been achieved.

According to the present disclosure, it has been discovered that anexcessive amount of compression or strain on the tissue may result inthe tissue having insufficient blood flow thereto in order to achieve anacceptable hemostasis and/or tissue fusion. An insufficient flow ofblood to the tissue may result in tissue necrosis or the like.Additionally, it has been discovered that an insufficient amount ofcompression or strain on the tissue may result in the tissue having toomuch blood flow thereto in order to achieve an acceptable hemostasisand/or tissue fusion. Too much blood flow to the tissue may result inthe tissue “bleeding out”.

The recorded compression or strain of the tissue is compared to anexisting record or data look-up table of acceptable tissue compressionsand/or strains for different tissues. The gap between the cartridgeassembly 20 and the anvil assembly 22 is adjusted until the compressionand/or strain on the tissue is within an acceptable range.

Once the desired strain on the tissue is achieved, surgical instrument10 is fired using either a universal-type staple or staplesappropriately sized for the thickness of the tissue clampedtherebetween. The strain on the tissue is determined using knownformulas based upon initial/compressed tissue thickness. Reference maybe made to U.S. application Ser. No. 11/409,154, filed on Apr. 21, 2006,the entire content of which is incorporated herein by reference, for amore detailed discussion of the determination of strain on tissue.

Reference may be made to U.S. Pat. No. 6,817,508, the entire content ofwhich is incorporated herein by reference, for a more detaileddiscussion of the structure and operation of surgical instrument 10.

Turning now to FIGS. 7-11, a surgical instrument according to anotherembodiment of the present disclosure is generally designated as 100. Asseen in FIG. 7, surgical instrument 100 includes a proximal handleassembly 112, an elongated central body portion 114 including a curvedelongated outer tube 114 a, and a distal head portion 116. Alternately,in some surgical procedures, e.g., the treatment of hemorrhoids, it isdesirable to have a substantially straight, preferably shortened,central body portion. The length, shape and/or the diameter of bodyportion 114 and head portion 116 may also be varied to suit a particularsurgical procedure.

Handle assembly 112 includes a stationary handle 118, a firing trigger120, a rotatable approximation knob 122 and an indicator 124. Stationaryhandle 118 defines a housing for the internal components of handleassembly 112. The internal components of handle portion 112 will bediscussed in detail below. Preferably, cushioned and/or resilient slipresistant portions such as a grip (not shown) can be fastened to orincluded as part of stationary handle 118 and firing trigger 120. Apivotally mounted trigger lock 126 is fastened to handle assembly 112and is manually positioned to prevent inadvertent firing of surgicalinstrument 100. Indicator 124 is positioned on the stationary handle 118and includes indicia, e.g., color coding, alpha-numeric labeling, etc.,to identify to a surgeon whether the device is approximated and is readyto be fired. Head portion 116 includes an anvil assembly 130 and a shellassembly 131. Each of these assemblies will be discussed in detailbelow.

Turning now to FIG. 8, the internal components of handle assembly 112include and are not limited to the proximal components of anapproximation and firing mechanism, a firing lockout mechanism and anindicator drive mechanism.

Referring to FIG. 8, the approximation mechanism includes approximationknob 122, a drive screw 132, a rotatable sleeve 133, and an anvilretainer 138 (see FIG. 7) for supporting an anvil assembly 130.Rotatable sleeve 133 includes a substantially cylindrical hollow bodyportion 140 and a substantially cylindrical collar 142 which togetherdefine a central bore. Collar 142 has an annular groove 144 formedthereabout which is dimensioned to receive an inwardly extending flangeformed on an inner wall of handle assembly 118. Engagement betweengroove 144 and the flanges axially fixes sleeve 133 within handleassembly 118 while permitting rotation of sleeve 133 in relation tohandle assembly 118. A pair of diametrically opposed elongated ribs 148are positioned or formed on the outer surface of body portion 140.Approximation knob 122 includes a pair of internal slots (not shown)positioned to receive ribs 148 of sleeve 133 to rotatably fix sleeve 133to knob 122, such that rotation of knob 122 causes concurrent rotationof sleeve 133.

The proximal half of screw 132 includes a helical channel 150 and isdimensioned to be slidably positioned within the central bore ofrotatable sleeve 133. Since sleeve 133 is axially fixed with respect tohandle assembly 118, rotation of sleeve 133 about screw 132 causes a pin(not shown) to move along channel 150 of screw 132 to effect axialmovement of screw 132 within handle assembly 118.

In operation, when approximation knob 122 is manually rotated, rotatablesleeve 133 is rotated about the proximal end of screw 132 to move a pinalong helical channel 150 of screw 132. Since sleeve 133 is axiallyfixed to handle assembly 118, as the pin is moved through channel 150,screw 132 is advanced or retracted within handle assembly 118. As aresult, top and bottom screw extensions (not shown), which are fastenedto the distal end of screw 132, and to anvil retainer 138, are movedaxially within elongated body portion 114. Since anvil assembly 130 issecured to the distal end of anvil retainer 138, rotation ofapproximation knob 122 will effect movement of anvil assembly 130 inrelation to shell assembly 131 between spaced and approximatedpositions.

With continued reference to FIG. 8, an LVDT 170 (Linear VariableDifferential Transformer) is provided in handle assembly 118 fordetermining a gap distance between anvil assembly 130 and shell assembly131. In particular, LVDT 170 may include a coil 174 disposed withinrotatable sleeve 133 and a magnet core 172 may be placed within coil174. Generally, as magnet core 172 moves back through the collar/handleassembly 118 the magnet core 172 gets closer/further to/from coil 174and produces an electrical output. In one embodiment, magnet core 172may include a screw having a magnet supported thereon or therein.

In operation, as approximation knob 122 is rotated to approximate anvilassembly 130 towards shell assembly 131, LVDT 170 functions to measureand determine the distance between the contacting surfaces of anvilassembly 130 and shell assembly 131.

Turning now to FIGS. 7 and 9-11, surgical instrument 100 includes aplurality of contact sensors 160, 162 placed along the length of atissue contacting surface of each of shell assembly 131 and anvilassembly 130. Contact sensors 160,162 are connected to the processor orCPU (see FIG. 1) and provide indication as to when an object, such as,tissue, is located between shell assembly 131 and anvil assembly 130. Inoperation, once initial contact is made between contact sensors 160,162and the tissue LVDT 170 may be used to determine and/or measure the gapbetween shell assembly 131 and anvil assembly 130.

With continued reference to FIGS. 7 and 9-11, surgical instrument 100may further include at least one force measuring sensor 164 provided ona surface of the head of anvil assembly 130, preferably oriented in aradially outward direction from an outer rim thereof, and at least oneforce measuring sensor 166 provided on an outer surface of shellassembly 131. Each force measuring sensor 164, 166 functions to measureforces acting thereon as a result of tissue pressing thereagainst, aswill be discussed in greater detail below.

As seen in FIG. 7, in one embodiment, surgical instrument 100 mayinclude a gauge 140 supported on stationary handle 118 of handleassembly 112. Each sensor 160, 162, 164, 166 may be operativelyconnected to gauge 140. Gauge 140 functions to display, in real time,selected operational parameters, such as, for example, tissue contact,tissue compression, tissue tension, etc.

In operation, following purse string suturing of a first tissue “T1” toanvil assembly 130 and purse string suturing of a second tissue “T2” toshell assembly 131 (as seen in FIG. 9), approximation knob 122 isrotated to approximate anvil assembly 130 towards shell assembly 131. Asanvil assembly 130 and shell assembly 131 are approximated toward oneanother, first and second tissue “T1, T2” are extended toward oneanother and are tensioned. As first and second tissue “T1, T2” aretensioned, first and second tissue “T1, T2” tend to constrict aroundanvil assembly 130 and shell assembly 131, respectively. Thisconstriction exerts a force on each respective force measuring sensor164, 166. The force measured by each force measuring sensor 164, 166 maybe converted, using known algorithms, to a value of tension force whichis being exerted on each tissue “T1, T2”.

During a surgical anastomotic procedure, the tension on first and secondtissues “T1, T2” is monitored in an attempt to maintain the tensionexerted thereon at or below a predetermined threshold level. Forexample, if the tension exerted on each tissue “T1, T2”, either alone orin combination, exceeds a predetermined threshold level, said elevatedtension acts on the staple line and may result in undue strains exertedon the staples and/or the staple line.

In one embodiment, as seen in FIG. 11A, surgical instrument 100 includesat least one plunger sensor 164 a provided on and extending radiallyoutwardly from the head of anvil assembly 130, and at least one plungersensor 166 a provided on and extending outwardly from shell assembly131. Each plunger sensor includes a pin 164 b, 166 b, respectively,slidably projecting from respective anvil assembly 130 and shellassembly 131, shown in phantom in FIG. 11A.

In operation, when a relatively low amount of tension is exerted onplunger sensors 164 a, 166 a, pins 164 b, 166 b thereof are in asubstantially extended condition, as shown in phantom in FIG. 11A.However, as first and second tissue “T1, T2” are tensioned, first andsecond tissue “T1, T2” tend to constrict around anvil assembly 130 andshell assembly 131, respectively, thus causing pins 164 b, 166 b of eachrespective plunger sensor 164 a, 166 a to be pressed radially inward.The displacement of pins 164 b, 166 b is used to calculate and/orextrapolate the degree of tension being exerted on first and secondtissue “T1, T2”.

Reference may be made to U.S. patent application Ser. No. 10/528,975,filed Mar. 23, 2005, the entire content of which is incorporated hereinby reference, for a more detailed discussion of the structure andoperation of surgical instrument 100 and of a magnetic field sensor.

Turning now to FIGS. 12-14, a surgical instrument according to anotherembodiment of the present disclosure is generally designated as 200. Asseen in FIGS. 12-14, surgical instrument 200 includes a cartridgereceiving half-section 212, an anvil half-section 214 operativelycoupled to cartridge receiving half-section 212, a cartridge assembly216 configured and adapted to be removably mounted within a distal endof cartridge receiving half-section 212 and a firing slide 210configured and adapted to be slidably received within cartridgereceiving half-section 212. As seen in FIG. 13, with cartridge receivinghalf-section clamping lever 230 in an open position, a proximal end ofanvil half-section 214 is slidably and pivotably receivable at aproximal end of cartridge receiving half-section 212. Surgicalinstrument 200 includes mounting bosses 254, projecting from anvilhalf-section 214, are slidably and pivotably receivable within an accesschannel 236 a of or defined by cartridge receiving half-section clampinglever 230 in order to approximate a distal end of the cartridgereceiving and anvil half-sections 212, 214.

As seen in FIG. 12, anvil half-section 214 includes an anvilhalf-section channel member 250 having a substantially U-shapedcross-sectional profile. Anvil half-section 214 is provided with ananvil plate 244 configured and dimensioned to be fit over anvilhalf-section channel member 250 of anvil half-section 214. Anvil plate244 includes a plurality of anvil pockets formed therein (not shown),arranged in two pairs of longitudinal rows, and an anvil knife track(not shown) formed longitudinally therealong.

As seen in FIG. 12, surgical instrument 200 includes a firing lever 265pivotably coupled thereto. Firing lever 265 is configured and adapted toprovide a user with the ability to fire surgical instrument 200 fromeither the left or the right side thereof.

One method or sequence of coupling and closure of cartridge receivinghalf-section 212 with anvil half-section 214 is best seen in FIGS. 13and 14. With cartridge lever 230 in an open position, as seen in FIG.13, the proximal ends of half-section 212, 214 are approximated towardone another such that a pivot limiting pin 296 of anvil half-section 214rests within pivot pin receiving slots of pivot plates (not shown) ofcartridge receiving half-section 212. The shape of pivot limiting pin296 limits the longitudinal angle (i.e., the angle between cartridgereceiving half-section 212 and anvil half-section 214) at which anvilhalf-section 214 can be coupled with cartridge receiving half-section212. With the proximal ends of half-section 212, 214 coupled to oneanother, the distal ends of half-section 212, 214 (or the end effector)are approximated towards one another until the mounting bosses 254, arereceived within access channels 236 a of clamping lever 230 (see FIG.12).

With the mounting bosses positioned within access channels 236 a ofcartridge lever 230, as seen in FIG. 14, the proximal end of clampinglever 230 is approximated toward cartridge receiving half-section 212until a catch 226 of cartridge receiving half-section 212 engages alatch 224 of cartridge receiving half-section channel member 230 (seeFIG. 13). By approximating clamping lever 230 toward cartridge receivinghalf-section 212, the mounting bosses are advanced through accesschannels 236 a thereby completing the approximation of cartridgereceiving half-section 212 with anvil half-section 214.

Reference may be made to U.S. patent application Ser. No. 10/508,191,filed Sep. 17, 2004, the entire content of which is incorporated hereinby reference, for a more detailed discussion of the structure andoperation of surgical instrument 200.

As seen in FIGS. 12-14, surgical instrument 200 includes gap sensingand/or measuring elements (e.g., magneto-resistive elements) 260 placedalong at least a portion of the length of the distal ends of each of thecartridge receiving half-section 212 and the anvil half-section 214. Gapmeasuring elements 260 may be placed along an outer surface and/or alongan inner surface of each of the cartridge receiving half-section 212 andthe anvil half-section 214.

Surgical instrument 200 further includes contact sensing elements 262placed along the tissue contacting surfaces of each of the anvil plate244 and the cartridge assembly 216. In this manner, as surgicalinstrument 200 is being clamped onto target tissue, the contact sensingelements 262 will provide the user with an indication (i.e., audio,visual, tactile, etc.) as to when the target tissue is initially broughtinto contact with the tissue contacting surfaces of each of the anvilplate 244 and the cartridge assembly 216. In one embodiment, it isdesirable to determine when the tissue contacts solely a distal end ofanvil plate 244 and/or cartridge assembly 216.

As seen in FIGS. 13 and 14, surgical instrument 200 further includesforce sensing and/or measuring elements 264 (e.g., strain gauges, loadcells, etc.) placed along at least a portion of the length of the distalends of each of the cartridge receiving half-section 212 and the anvilhalf-section 214. In this manner, in operation, force sensing and/ormeasuring elements 264 are capable of transmitting measurements of theclamping forces being applied to the target tissue by the distal ends ofthe cartridge receiving half-section 212 and the anvil half-section 214.

Turning now to FIGS. 15-19, a surgical instrument according to anotherembodiment of the present disclosure is generally designated as 300. Asseen in FIGS. 15 and 16, surgical instrument 300 includes a handleassembly 312 and an elongated body 314. As illustrated in FIGS. 15 and16, the length of elongated body 314 may vary to suit a particularsurgical procedure. A disposable loading unit or DLU 316 is releasablysecured to a distal end of elongated body 314. DLU 316 includes aproximal body portion 318, which forms an extension of elongated body314, and a distal tool assembly or end effector 320 including a firstmember or cartridge assembly 322 and a second member or anvil assembly324. Tool assembly 320 is pivotably connected to body 318 about an axissubstantially perpendicular to the longitudinal axis of elongated body314. Cartridge assembly 322 houses a plurality of staples. Anvilassembly 324 is movable in relation to cartridge assembly 322 between anopen position spaced from cartridge assembly 322 and an approximated orclamped position in juxtaposed alignment with cartridge assembly 322.The staples may be housed in cartridge assembly 322 to apply linear rowsof staples having a length measuring from about 30 mm to about 60 mm,although other staple configurations and lengths are envisioned.

Handle assembly 312 includes a stationary handle member 326, a movablehandle or trigger 328 and a barrel portion 330. A rotatable member 332is rotatably mounted to the forward end of barrel portion 330 andsecured to elongated body 314 to facilitate rotation of elongated body314 in relation to handle assembly 312. An articulation lever 330 a issupported on a distal portion of barrel portion 330 and is operable, ina manner to be described hereafter, to effect articulation of toolassembly 320 with respect to body portion 318 of DLU 316. A pair ofreturn knobs 336 are movably supported along barrel portion 330 toeffect movement of surgical instrument 300 from an advanced position toa retracted position.

As seen in FIGS. 17-19, surgical instrument 300 includes an axial driveassembly 312 including a distal working head 368. A distal end ofworking head 368 supports a cylindrical cam roller 386. Cam roller 386is dimensioned and configured to engage a cam surface 309 of anvilassembly 324 to clamp anvil assembly 324 against body tissue “T”.

In operation, to approximate the cartridge and anvil assemblies 322 and324, movable handle 328 is moved toward stationary handle 326, throughan actuation stroke. Subsequent movement of movable handle 328 throughthe actuation stroke effects advancement of an actuation shaft and afiring rod (not shown). As the actuation shaft is advanced, so to is thefiring rod.

The firing rod is connected at its distal end to axial drive assembly312 such that advancement of the firing rod effects advancement of driveassembly 312. As drive assembly 312 is advanced, cam roller 386 movesinto engagement with cam surface 309 of anvil assembly 324 (see FIGS. 17and 18) to urge anvil assembly 324 toward cartridge assembly 322,thereby approximating cartridge and anvil assemblies 322 and 324 andclamping tissue “T” therebetween.

To fire surgical instrument 300, movable handle 328 is moved through asecond actuation stroke to further advance the actuation shaft and thefiring rod distally. As the firing rod is advanced distally, driveassembly 312 is advanced distally to advance actuation sled 334 throughstaple cartridge assembly 322 to simultaneously sever tissue with knife380 (see FIGS. 17-19) and drive pushers 348 to sequentially ejectstaples “S” from cartridge assembly 322.

Surgical instrument 300 is adapted to receive DLU's having staplecartridges with staples in linear rows having a length of from about 30mm to about 60 mm. For example, each actuation stroke of movable handle328 during firing of surgical instrument 300 may advance the actuationshaft approximately 15 mm, although other lengths are envisioned.Accordingly, to fire a cartridge assembly having a 45 mm row of staples,movable handle 328 must be moved through three actuation strokes afterthe approximating or clamping stroke of movable handle 328.

Reference may be made to U.S. patent application Ser. No. 10/490,790,filed Mar. 24, 2004, the entire content of which is incorporated hereinby reference, for a more detailed discussion of the structure andoperation of surgical instrument 300.

As best seen in FIGS. 16-18, surgical instrument 300 includes gapsensing and/or measuring elements (e.g., magneto-resistive elements) 360placed along at least a portion of the length of the distal ends of eachof the cartridge assembly 322 and the anvil assembly 324. Gap measuringelements 360 may be placed along an outer surface and/or along an innersurface of each of the cartridge assembly 322 and the anvil assembly324.

Surgical instrument 300 further includes contact sensing elements 362placed along the tissue contacting surfaces of each of the anvilassembly 324 and the cartridge assembly 322. In this manner, as surgicalinstrument 300 is being clamped onto target tissue “T”, the contactsensing elements 362 will provide the user with an indication (i.e.,audio, visual, tactile, etc.) as to when the target tissue is initiallybrought into contact with the tissue contacting surfaces of each of theanvil assembly 324 and the cartridge assembly 322.

As seen in FIGS. 17 and 18, surgical instrument 300 further includesforce sensing and/or measuring elements 364 (e.g., strain gauges, loadcells, etc.) placed along at least a portion of the length of the distalends of each of the cartridge assembly 322 and the anvil assembly 324.In this manner, in operation, force sensing and/or measuring elements364 are capable of transmitting measurements of the clamping forcesbeing applied to the target tissue by the distal ends of the cartridgeassembly 322 and the anvil assembly 324. Reference may be made to U.S.application Ser. No. 11/409,154, filed on Apr. 21, 2006, the entirecontent of which is incorporated herein by reference, for a moredetailed discussion of force sensing and/or measuring elements, such asload cells and/or strain gauges.

In an embodiment, capacitive elements may be used to determine the gapbetween the jaw members of the surgical instrument. For example, a platemay be mounted on, or near, each side of the jaw members such thatmovement of the jaw members changes the gap between the plates of thecapacitive element or the amount of shared area, or overlap, of theplates of the capacitive element. By applying a voltage between theplates a capacitor and an electric field may be formed between theplates. The potential applied to the plates, the gap between the platesand the amount of overlap of the plates would thus enable the capacitorto store energy and to determine the strength and size of the electricfield. Motion of the jaw members may be translated into a change incapacitance and a change in the electric field. Either or both may bemeasured and used to determine the separation distance or movement ofthe jaw members.

In another embodiment, any of the aforementioned surgical instrumentsmay include and/or incorporate the use of electromagnetic inductionsensors in order to determine the gap. Electromagnetic induction sensorsmay be used to detect changes in sensor coil impedance resulting from achange in distance between the sensor coil and a conductive targetmaterial. For example, a coil driven by an alternating current maygenerate an oscillating magnetic field that, in turn, induces eddycurrents in a target metallic object. The eddy currents move in adirection opposite the current of the coil thereby reducing magneticflux in the coil and its inductance. Eddy currents also dissipate energyincreasing the coil's resistance. In use, resistance increases andinductance decreases as the target approaches the coil. These changes inresistance and inductance are proportional to the distance and are thebasis of position sensing when using electromagnetic induction sensors.

In still another embodiment, any of the aforementioned surgicalinstruments may include and/or incorporate the use of inductive sensors,such as linear variable differential transformers (LVDT's), to transducemotion into an electrical signal in order to determine the gap. Movementof the elements of surgical instrument including inductive sensors,relative to each other, alters an overall inductance or inductivecoupling. These changes in inductance or inductive coupling may bedetected and are the basis for LVDT position sensing.

In yet another embodiment, any of the aforementioned surgicalinstruments may include and/or incorporate the use of thin film giantmagnetoresistive (GMR) materials that are placed adjacent to a sourcefor producing a magnetic field. For example, the GMR and the source forproducing the magnetic field may be placed on respective ones of the jawmembers of the surgical instrument. Accordingly, the distance from theGMR material to the source for producing the magnetic field would varywith changes in the size of the gap between the jaw members. A thin filmGMR material may include two layers of magnetic material. The electricalconductivity of each layer is dependent upon the magnetic alignment ofthe individual layers and on the spin of the individual electrons. Alayer with a particular magnetic alignment will only allow electrons ofa particular spin to pass. If the layers are not in alignment, electronswith a particular spin pass through one layer, but not the other, so theoverall resistance is high. If the layers are in magnetic alignment,which occurs when GMR film is placed in a magnetic field, both layersare permeable to electrons with the same spin and resistancetherethrough is decreased. The layers electrical conductivity depositedon silicone substrates can be configured as resistors in a variety ofconfigurations, the most common of which is the Wheatstone bridge. Thedistance from the GMR to the source for producing the magnetic field iscalculated based on the relationship between field strength anddistance.

In an embodiment, any of the aforementioned surgical instruments mayinclude and/or incorporate the use of Hall effect sensors to determinethe size of the gap between the jaw members. Hall effect sensors aresheets of semiconductor material across which a constant voltage isapplied and which conduct a constant bias current. The voltagedifference across the sheet on the axis perpendicular to the constantapplied voltage is proportional to the strength of the magnetic fieldthe sheet is exposed to. The distance from the sensor to the magnet isdetermined knowing the relationship between the field strength anddistance.

In another embodiment, the size of the gap between the jaw members ofany of the aforementioned surgical instruments may be determined byusing optical based sensors. One type of optical based sensor includes adiffuser sensor, which typically includes a light emitter and a lightreceiver that are placed in juxtaposed relation to one another. Thelight receiver measures the intensity of reflected light from the targettissue. The intensity of reflected light is related to the distancebetween the light emitter and the target tissue, and such distancetranslates to the stapler gap distance.

Another type of optical sensor includes a time-of-flight sensor.Time-of-flight sensors measure distance by dividing the velocity oflight by the time it takes for emitted light and/or the reflected lightto be detected by a receiver. A further type of optical sensor utilizestriangulation techniques. Triangulation is a measurement scheme by whicha laser projects a collimated beam that reflects off a target and passesthrough a lens that focuses the reflected beam onto a receiving element.Changes in distance between the sensor and target result in changes ofthe angle of the returning light and consequent change in the positionof the beam on the receiving array. The distance is determined by theposition of the beam on the receiving array.

In yet another embodiment, the size of the gap between the jaw membersof any of the aforementioned surgical instruments may be determined byutilizing ultrasonic sensors that measure distance by reflecting a knownvelocity of a sound-wave by one-half the time required for an emittedsound to reflect off a target and to return to the sensor. Theseultrasonic sensors may be incorporated into each jaw member of thesurgical instrument.

In still another embodiment, the linear motion of the jaw members of anyone of the aforementioned surgical instruments may be coupled to anadjustable variable resistor, or potentiometer (“POT”). A POT typicallyincludes a resistive element attached to a circuit via two fixedcontacts at each end of the resistive element and a third contact, orwiper that can slide between each end. The sliding contact divides thePOT into two resistors and the voltage across the two fixed contacts isdivided between each fixed contact and the wiper. The POT can beconfigured such that the linear motion is coupled to the position of thewiper such that the output voltage is directly related to a linearposition thereof.

As described supra, tissue contact or pressure sensors determine whenthe jaw members initially come into contact with the tissue “T”. Thisenables a surgeon to determine the initial thickness of the tissue “T”and/or the thickness of the tissue “T” prior to clamping. In any of thesurgical instrument embodiments described above, as seen in FIG. 20,contact of the jaw members with tissue “T” closes a sensing circuit “SC”that is otherwise open, by establishing contacting with a pair ofopposed plates “P1, P2” provided on the jaw members. The contact sensorsmay also include sensitive force transducers that determine the amountof force being applied to the sensor, which may be assumed to be thesame amount of force being applied to the tissue “T”. Such force beingapplied to the tissue, may then be translated into an amount of tissuecompression. The force sensors measure the amount of compression atissue is under and provide a surgeon with information about the forceapplied to the tissue “T”. Excessive tissue compression may have anegative impact on the tissue “T” being operated on. For example,excessive compression of tissue “T” may result in tissue necrosis and,in certain procedures, staple line failure. Information regarding thepressure being applied to tissue “T” enables a surgeon to betterdetermine that excessive pressure is not being applied to tissue “T”.

Any of the contact sensors disclosed herein may include, and are notlimited to, electrical contacts placed on an inner surface of a jawwhich, when in contact with tissue, close a sensing circuit that isotherwise open. The contact sensors may also include sensitive forcetransducers that detect when the tissue being clamped first resistscompression. Force transducers may include, and are not limited to,piezoelectric elements, piezoresistive elements, metal film orsemiconductor strain gauges, inductive pressure sensors, capacitivepressure sensors, and potentiometric pressure transducers that usebourbon tubes, capsules or bellows to drive a wiper arm on a resistiveelement.

In an embodiment, any one of the aforementioned surgical instruments mayinclude one or more piezoelectric elements to detect a change inpressure occurring on the jaw members. Piezoelectric elements arebi-directional transducers which convert stress into an electricalpotential. Elements may consist of metallized quartz or ceramics. Inoperation, when stress is applied to the crystals there is a change inthe charge distribution of the material resulting in a generation ofvoltage across the material. Piezoelectric elements may be used toindicate when any one or both of the jaw members makes contact with thetissue “T” and the amount of pressure exerted on the tissue “T” aftercontact is established.

In an embodiment, any one of the aforementioned surgical instruments mayinclude or be provided with one or more metallic strain gauges placedwithin or upon a portion of the body thereof. Metallic strain gaugesoperate on the principle that the resistance of the material dependsupon length, width and thickness. Accordingly, when the material of themetallic strain gauge undergoes strain the resistance of the materialchanges. Thus, a resistor made of this material incorporated into acircuit will convert strain to a change in an electrical signal.Desirably, the strain gauge may be placed on the surgical instrumentssuch that pressure applied to the tissue effects the strain gauge.

Alternatively, in another embodiment, one or more semiconductor straingauges may be used in a similar manner as the metallic strain gaugedescribed above, although the mode of transduction differs. Inoperation, when a crystal lattice structure of the semiconductor straingauge is deformed, as a result of an applied stress, the resistance ofthe material changes. This phenomenon is referred to as thepiezoresistive effect.

In yet another embodiment, any one of the aforementioned surgicalinstruments may include or be provided with one or more inductivepressure sensors to transduce pressure or force into motion of inductiveelements relative to each other. This motion of the inductive elementsrelative to one another alters the overall inductance or inductivecoupling. Capacitive pressure transducers similarly transduce pressureor force into motion of capacitive elements relative to each otheraltering the overall capacitance.

In still another embodiment, any one of the aforementioned surgicalinstruments may include or be provided with one or more capacitivepressure transducers to transduce pressure or force into motion ofcapacitive elements relative to each other altering an overallcapacitance.

In an embodiment, any one of the aforementioned surgical instruments mayinclude or be provided with one or more mechanical pressure transducersto transduce pressure or force into motion. In use, a motion of amechanical element is used to deflect a pointer or dial on a gauge. Thismovement of the pointer or dial may be representative of the pressure orforce applied to the tissue “T”. Examples of mechanical elements includeand arc not limited to bourbon tubes, capsules or bellows. By way ofexample, mechanical elements may be coupled with other measuring and/orsensing elements, such as a potentiometer pressure transducer. In thisexample the mechanical element is coupled with a wiper on the variableresistor. In use, pressure or force may be transduced into mechanicalmotion which deflects the wiper on the potentiometer thus changing theresistance to reflect the applied pressure or force.

The combination of the above embodiments, in particular the combinationof the gap and tissue contact sensors, provides the surgeon withfeedback information and/or real-time information regarding thecondition of the operative site and/or target tissue “T”. For example,information regarding the initial thickness of the tissue “T” may guidethe surgeon in selecting an appropriate staple size, informationregarding the clamped thickness of the tissue “T” may let the surgeonknow if the selected staple will form properly, information relating tothe initial thickness and clamped thickness of the tissue “T” may beused to determine the amount of compression or strain on the tissue “T”,and information relating to the strain on the tissue “T” may be usedthis strain to avoid compressing tissue to excessive strain valuesand/or stapling into tissue that has undergone excessive strain.

Additionally, force sensors may be used to provide the surgeon with theamount of pressure applied to the tissue. The surgeon may use thisinformation to avoid applying excessive pressure on the tissue “T” orstapling into tissue “T” which has experienced excessive strain.

With reference to FIGS. 1 and 4-6A, in addition to contact sensors 60,surgical instrument 10 may include strain gauges 62 placed along thelength of the tissue contact surface of each of cartridge assembly 20and anvil assembly 22.

As seen in FIGS. 1, 7, 12 and 15, any of the aforementioned surgicalinstruments may be selectively electrically connected to a centralprocessing unit (CPU), an e-motor (electronic motor) or the like formonitoring, controlling, processing and/or storing information observed,measured, sensed and/or transmitted from any of the elements ofcomponents of the surgical instruments prior, during and/or after thesurgical procedure.

It will be understood that various modifications may be made to theembodiments disclosed herein. Therefore, the above description shouldnot be construed as limiting, but merely as exemplifications ofpreferred embodiments. Those skilled in the art will envision othermodifications within the scope and spirit of the claims appended hereto.

1. A surgical instrument for operating on tissue, comprising: an endeffector including a first tissue engaging member and a second tissueengaging member in juxtaposed relation to the first tissue engagingmember; and a gap determination element operatively associated with thesurgical instrument for measuring a gap distance between the firsttissue engaging member and the second tissue engaging member, the gapdetermination element generating a first voltage corresponding to afirst condition of the gap determination element and generating a secondvoltage corresponding to a second condition of the gap determinationelement, wherein the first condition of the gap determination element isindicative of the first and second tissue engaging surfaces being in aspaced-apart position and the second condition of the gap determinationelement is indicative of the first and second tissue engaging surfacesbeing in an approximated position.
 2. The surgical instrument accordingto claim 1, wherein the gap determination element is remotely locatedfrom the end effector assembly and movable relative thereto.
 3. Thesurgical instrument according to claim 1, further including a tissuecontact determining element that is operatively associated with arespective tissue contacting surface of at least one of the first tissueengaging member and the second tissue engaging member.
 4. The surgicalinstrument according to claim 1, further including a processor inoperative communication with the gap determination element andconfigured to measure the first and second voltages.
 5. The surgicalinstrument according to claim 4, wherein the processor is operativelyconnected to the gap determination element and to each of the tissuecontact determining elements.
 6. The surgical instrument according toclaim 1, wherein each of the first and second tissue engaging membersincludes at least one tissue contact determining element supported onthe tissue contacting surface thereof.
 7. The surgical instrumentaccording to claim 1, wherein the gap determination element is selectedfrom the group consisting of a slide potentiometer, a rotationalpotentiometer, a linear variable differential transformer, amagneto-resistive element, capacitive elements, electromagneticinduction sensors, Hall effect sensors, and optical based sensors. 8.The surgical instrument according to claim 1, wherein the tissue contactdetermining element is selected from the group consisting of pressuresensors, electrical contacts and sensing circuits, force transducers,piezoelectric elements, piezoresistive elements, metal film straingauges, semiconductor strain gauges, inductive pressure sensors,capacitive pressure sensors, and potentiometric pressure transducers. 9.The surgical instrument according to claim 1, wherein the surgicalinstrument is a stapler.
 10. The surgical instrument according to claim4, wherein the tissue contact determining element transmits a signal tothe processor when a tissue is positioned between the first and secondtissue engaging elements and when the tissue contacting surface of eachof the first and second tissue engaging elements contacts the tissue.11. The surgical instrument according to claim 10, wherein the signaltransmitted to the processor, when the tissue contacting surface of eachof the first and second tissue engaging elements contacts the tissue, isindicative of tissue thickness.
 12. The surgical instrument according toclaim 11, wherein the processor is configured to monitor at least one ofa compression force and a strain on the tissue as the tissue iscompressed between the first and second tissue engaging members.
 13. Thesurgical instrument according to claim 12, wherein the processor isconfigured to activate a signal when at least one of the compressionforce and strain on the tissue achieves a predetermined level ofcompression or strain.
 14. The surgical instrument according to claim13, wherein the predetermined level of compression or strain on thetissue is maintained in a data look-up table.
 15. The surgicalinstrument according to claim 14, wherein the data look-up tableincludes predetermined levels of compression or strain for numeroustissue types.
 16. The surgical instrument according to claim 13, whereinthe predetermined level of compression or strain is a percentage of theinitial tissue thickness.
 17. The surgical instrument according to claim1, further comprising at least one first force measuring sensor providedon a surface of the first tissue engaging member, wherein each firstforce measuring sensor is oriented in an outward direction from an outersurface thereof, and at least one second force measuring sensor providedon the second tissue engaging member, wherein each second forcemeasuring sensor is oriented in an outward direction from an outersurface thereof.
 18. The surgical instrument according to claim 17,wherein each first and second force measuring sensor functions tomeasure forces acting thereon as a result of tissue pressingthereagainst.
 19. The surgical instrument according to claim 17, furthercomprising a gauge operatively connected to each of the first and secondforce measuring sensors.